Numerical Simulation of Blocking and Abnormal Weater in General Circulation

大气异常天气与阻塞高压的发生密切相关。因此，了解阻塞对于研究扩展范围预测是很重要的。本文采用一个简单的正压模型对阻塞进行了一系列数值模拟，该模型采用了一个造波器作为斜压不稳定性的参数化。结果表明，该模型成功地模拟了阻塞的生命周期。在模式大气中，天气扰动被造波器以指数方式放大。随着与罗斯比波破裂有关的从天气波到行星波的能量非线性散射，指数增长很快饱和。位涡度（PV）分析表明，阻塞的发生是由罗斯比波破碎引起的。高低pv的翻转在地形固定脊处倾向于出现。一旦罗斯比波浪破碎形成一个块体。随后。波浪被它阻挡并经历子午拉伸。被拉伸的波随后分解。将新鲜的低PV沉积在阻塞系统的北部，将高PV沉积在阻塞系统的南部以维持阻塞。结果与所谓的涡流应变机制一致。结果表明，天气扰动的指数增长对于阻塞的发生和维持都是必不可少的。

Abnormal weather in the atmosphere is closely related to tlie occurrence of block-ing high. Understanding of blocking is thus important for the study of extended-range forecasting. In this study, a series of numerical simulations of blocking is conducted using a simple barotropic model which implements a wavemaker as a parametarization of baroclinic instability. It is shown that the model successfuly simulates the life-cycle of blocking.In the model atmosphere, the synoptic disturbances are amplified exponentially by the wavemaker. The exponential growth soon saturates with nonlinear scattering of energy from synoptic to planetary waves associated with a Rossby wave breaking. The analysis of potential vorteity (PV) indisates that the onset of blocking in brought by the Rossby wave breaking. The overturning of high and low PVs tends to oeeur at the topographic stationary ridge.Once a block is formed by the Rossby wave breaking. subsequent. Ross by waves are blocked by it and undergo meridional stretch. The stretched wave then breaks down. depositing fresh low PV at the north and high PV at the south of the blocking system to maintain the block. The result is consistent with the so-called eddy straining mechanism. It is suggested from the result that the expouential growth of synoptic disturbances is esscetial both for the onset and the maintenance of blocking.